One of the first scientific depictions of the lever principle – on which all pliers are based – is found in the treatise on mechanics which is ascribed to the Greek philosopher Aristotle (384-322 BC). "In the section on the lever both the force and the load are seen as weights and accordingly as directly comparable variables. This made it possible for Aristotle to formulate the principle of the lever: the relationship of the moved weight to the moving weight is in reverse proportion to the relationship of the lengths of the corresponding lever arms to another: this means that the further a force is from the fulcrum of the lever, the easier it can move something (850a30 et seqq. ). Aristotle used this universally valid statement again and again in the following chapters as a basis for analysing different technical instruments and devices; oars and rudders, dentist’s pliers and the nutcracker are recognised as levers or combinations of levers and explained by means of the law of the lever."
(Helmuth Schneider, Einführung in die Antike Technikgeschichte [Introduction to the History of Ancient Technology], Darmstadt 1992)

These illustrations show pages from an edition of the "Mechanics" from 1599.